1. Field of the Invention
The present invention relates to a current control circuit, disposed between a primary terminal and a secondary terminal, for controlling a current flowing from the primary terminal to the secondary terminal.
2. Description of the Related Art
Hitherto, there is known a rush current preventing circuit, disposed between a source output terminal of a power supply and a source input terminal of an arbitrary electronic circuit, for preventing a rush current so that an output of the power supply does not exceed a predetermined rated output.
Further, there is known an overcurrent detection circuit for detecting an overcurrent to prevent fumes and going up in flames from occurring even if the electronic circuit of the secondary is subjected to a short-circuit and the like, while a sufficient current is supplied even if the maximum load is involved within a usual operating range of the electronic circuit of the secondary.
FIG. 4 is a circuit diagram of a current control circuit according to an embodiment of the present invention. a circuit diagram showing a state that both the rush preventing circuit and the overcurrent detection circuit are provided.
Usually, a considerably large capacity of capacitor C is disposed at the secondary. At the time of a power supply is turned on, a rush current will occur for a charge of the capacitor C and the like. The rush preventing circuit is disposed to prevent the primary power supply from being damaged by the rush current. Further, the overcurrent detection circuit is connected in series to the rush preventing circuit to prevent an overcurrent from conducting when an electronic circuit connected to the secondary is subjected to a short-circuit and the like. When the overcurrent detection circuit detects the overcurrent, a detection result is transmitted to an overcurrent recognition circuit (not illustrated). Thus, the overcurrent recognition circuit recognizes that the overcurrent, which is not to be accepted, conducts. And then the overcurrent is suppressed by an overcurrent control circuit (also not illustrated).
According to the circuit constitution as shown in FIG. 4, both the rush preventing circuit and the overcurrent detection circuit are provided on a current path directed from the primary to the secondary. This constitution brings about power loss on the respective circuits and voltage drop at the secondary. This causes shortage of ability in operation for the electronic circuits connected to the secondary, or alternatively increments of a circuit scale and a circuit cost for suppressing power loss on the rush preventing circuit and the overcurrent detection circuit to avoid the occurrence of the shortage of ability in operation for the electronic circuits.
Individual provision of the rush preventing circuit and the overcurrent detection circuit as shown in FIG. 4 brings about necessity for design and test of respective circuits. This involves an increment of process.